The instant invention is a device which enhances the recovery of a sheet of memory metal beyond the inherent recovery of the memory metal comprising said sheet. Memory metals are alloys which manifest the shape--memory effect--such alloys are well known and they, and the shape--memory effect, are discussed in e.g., "Shape--Memory Alloys", Scientific American, v. 281, pp 74/82 (November 1979). In the past such memory metals have been utilized in mechanical composite pipe couplings to force tensile load-bearing members into gripping contact with pipes and tubing. Commonly assigned Australian Pat. No. 74153/74 to C. L. Martin discloses the use of such memory metals as drivers to be utilized externally and internally with respect to pipes. The recovery capability of the memory metal in such cases is limited to the inherent recovery of the memory metal comprising said drivers, which is in the range of 4-9% maximum for solid metal members. Commonly assigned British Pat. No. 1,554,431 to C. L. Martin discloses the use of various configurations of memory metal alloy to secure patch members over ruptured pipe sections. Martin discloses the use of a helical spring-like memory metal driver to achieve a higher degree of recovery in the radial direction. Likewise, commonly assigned U.S. Pat. No. 4,197,880 to J. M. Cordia discloses a compressed, axially slit, cylindrical memory metal driver member which is held is a radially compressed configuration by a thermoplastic retainer means, and is used to drive a foamable material toward the inside wall of a pipe. The driver disclosed by Cordia is axially slit to enhance its radial recovery. Neither of the Martin patents nor the Cordia patent suggest the construction of a highly articulated and therefore recoverable device comprising a sheet of memory metal having a plurality of perforations of related shape and pattern which will enhance the recovery beyond the inherent recovery of the memory metal comprising said sheet. Further, none of the above described references suggest a sheet which can be configured into a continuous geometric configuration, for example, a cylindrical shape having a continuous circumference necessary for the application of truly uniform pressure. Further, because of the continuous circumference the cylindrical embodiment of the instant invention exerts greater pressure that the above described references. It should be apparent that the unique sheet of the instant invention is useful in a variety of geometric configurations of said sheet ranging from flat to, for example, cylindrical configurations, none of which are suggested in the above described references.
It is a primary object of the instant invention to provide a sheet of memory metal having enhanced recoverability beyond the inherent recovery of the memory metal comprising said sheet.
It is another object of the instant invention to provide a sheet of memory metal which is recoverable in substantially a single direction within the plane of said sheet.
It is yet another object of the instant invention to provide a sheet of memory metal which recoverable in more than one direction within the plane of said sheet.